1. Field of the Invention
This invention concerns removing sludge from a lubricating oil by contacting the oil with a dispersant functional group incorporated on an immobilized substrate through which the oil is passed.
2. Description of Related Art
During combustion of fuel (e.g. gasoline) in an internal combustion engine, certain polar hydrocarbon contaminants (e.g. low molecular weight polar alkyl compounds such as alcohols, aldehydes, ketones, carboxylic acids, and the like) are formed due to incomplete combustion of the fuel. These sludge and varnish precursors are passed into the lubricating oil with the combustion gases where the precursors contact water in the oil and agglomerate to form an emulsion which is commonly referred to as sludge. The presence of sludge in the oil is undesirable because it tends to increase the oil's viscosity, promote the presence of varnish in the oil, and plug oil ways.
For many years, dispersants have been used in lubricating oils to greatly increase the capacity of the oil to suspend sludge. This in turn decreases the sludge's detrimental effect on viscosity, varnish, and oil way plugging. However, at some point, an oil's capacity to protect an engine becomes limited, even with the most potent dispersant. In addition, dispersants in current use suspend sludge in such a finely divided form that the sludge passes through currently available filters and remains in the oil.
Therefore, it would be desirable to have available a simple, yet convenient method for removing sludge from a lubricating oil and thereby avoid the deleterious effects of leaving the sludge suspended in the oil.